This application claims priority to European Application Serial Number 00870164.1 filed on Jul. 14, 2000, the disclosure of which is incorporated herein by reference in its entirety.
The present invention relates to a process and a device for collecting oxygen-enriched air, which are intended to be used by a cryotechnic rocket engine for propelling a space launch rocket.
The present invention also relates to turbofan or turbocompressor type engines equipped with a collecting device.
Certain space launch rockets are equipped with hydrogen/oxygen cryotechnic rocket engines which are conventional engines known to those skilled in the art.
It is observed that, for a launch rocket equipped with such an engine, the mass of oxygen on take-off is considerable and may be between 15% and 75% of the total mass of the launch rocket.
The present invention thus comprises launching such launch rockets with empty or at least partially empty oxygen tanks and in filling them with air or more particularly with oxygen-enriched air which will be collected in the atmosphere during an aerobic flight sequence. The oxygen-enriched air is stored on-board during this phase. It is used by the cryotechnic rocket engine beyond the atmosphere.
To achieve this, collection systems have already been studied since the 1950s, and more particularly in the United States, where prototypes of subsystems at least have been produced.
In particular, document U.S. Pat. No. 3,756,024 describes this principle of in-flight collection with intake of air: coolingxe2x80x94liquefactionxe2x80x94nitrogen/oxygen separationxe2x80x94storage of the liquid oxygen or oxygen-enriched airxe2x80x94evacuation of the nitrogen or oxygen-depleted air.
Such collection devices or systems are composed substantially of an air intake, a compressor for compressing the air, exchangers and a separator. Several types of separators have been studied: rotary separators, vortex tube separators, paramagnetic separators, etc. The aim of the exchangers is to cool and condense the entering air, by means of the cooling capacity of a cryogenic fluid which may be hydrogen present on-board the launch rocket. The organization of the exchangers varies depending on the devices envisaged. The exchangers allow heat to be exchanged between the air and the hydrogen either directly or via another fluid flow such as helium or nitrogen. These exchangers may also allow the depleted air to be heated before it is ejected.
The aim of the separator is to separate the air entering into a flow of oxygen-enriched air and a flow of oxygen-depleted air, the flow of oxygen-enriched air being stored while the flow of oxygen-depleted air is expelled outside.
These are essentially systems that are independent of the propulsion even though they occasionally participate in the propulsion by appropriate ejection of the depleted air. They also have the following drawbacks: creation of a drag proportional to the output of processed air; need for an external or system-generated power supply; and, need for an air intake, a compressor and a propelling nozzle.
A collection system may be characterized by the collection rate, which is the amount of enriched air produced per kilo of hydrogen consumed, by the separation efficiency, which is the proportion of oxygen entering the collection system and which is collected, and by the oxygen concentration in the collected air.
To carry out the collection as presented above, it is necessary for a part of the flight to be propelled by an aerobic engine, that is to say an engine which uses atmospheric oxygen as an oxidant. It is proposed to use a turbofan engine on take-off and during the first stage of the flight up to a maximum of Mach 4. At Mach 4 or at a lower speed, a transition to propulsion by an engine of ramjet type may take place. In all cases, a final transition to propulsion by a rocket engine must take place, beyond the atmosphere, to achieve a speed sufficient for satellization.
The space launch rocket may be a single-stage rocket but is preferably a two-stage rocket, only the second stage coming into operation preferably at the time of the transition to rocket engine propulsion so as not to have to accelerate the aerobic engine(s) which are heavy.
U.S. Pat. No. 5,154,051 describes a liquefied air system with (crude) separation of the constituents of the air for several possible applications, the advantage of which is to be able to make the position of the air intake independent of the nozzle, allowing separation of the constituents of water. Separation of water prevents it from icing up in the system and the separation of O2-enriched air to allow storage for the purpose of collection or to be able to adjust the mix ratios in the combustion chamber during flight.
U.S. Pat. No. 3,002,340 describes a cycle of liquefied-air propulsion by integrating a liquefied-air system into a turbofan. However, no mention is ever made therein of collection strictly speaking comprising a cycle in which the air is compressed, cooled, liquefied, compressed again, heated and used in the gas generator.
The present invention aims to propose a process and a device for collecting oxygen-enriched air during the first phase of flight of a space launch rocket, which will be used as an oxidant for the rocket engine of this space launch rocket, this process and device not having the drawbacks of the prior art.
In addition, the present invention aims to provide a solution which is more effective, which consumes less energy, is of smaller volume or weight ratio, and which is less expensive than the solutions of the prior art.
In addition, the present invention aims to provide a solution which allows the thermodynamic and physical integration of a collection cycle with a turbofan engine used for the propulsion whereas, outside the collection phases, that is to say the phases of take-off and of low altitude, the turbofan engine is used conventionally.
The present invention aims to propose to directly integrate the collection device into the secondary flow of twin-flow propulsion engines, turbofan engines or turbojet engines used to propel space launch rockets during the first phase of the flight.
More particularly, the present invention aims to propose a process for collecting oxygen-enriched air during a phase of aerobic flight of a space launch rocket and which is intended to be used for combustion inside at least one cryotechnic rocket engine beyond the atmosphere. The launch rocket preferably comprises at least one engine of turbofan type. The turbofan engine is preferably a twin-spool and twin-flow engine and comprises a high-pressure spool consisting substantially of a high-pressure compressor, a combustion chamber in which the combustion of a cryotechnic fluid such as hydrogen takes place, turbines, and a low-pressure spool surrounding the high-pressure spool, consisting substantially of a blower for collecting the external fluid in the form of a main flow and a derived flow and a low-pressure turbine optionally followed by the after-burning area and a variable-geometry nozzle. The main flow is intended to follow the usual path of the various compression, combustion and depressurization cycles envisaged in the turbofan engine. The derived flow is subjected, after compression and cooling, to a separation in a separator for generating a flow of oxygen-enriched air and a flow of oxygen-depleted air. The flow of oxygen-enriched air is stored in order to be used for combustion inside a rocket engine, while the flow of oxygen-depleted air is ejected, preferably by being mixed with the main flow at the outlet of the low-pressure turbine.
Advantageously, the separation of the main flow and of the derived flow is carried out upstream of the fan and in the fan.
Preferably, the mixed flow passes into the after-burning area in which a flow of cryotechnic fluid is combusted before being ejected via the variable-geometry nozzle.
Advantageously, the derived flow undergoes a series of cooling/compression cycles carried out inside several exchangers and a cooling unit/condenser assembly.
According to one embodiment, before being collected by the blower, the derived flow undergoes cooling inside a heat exchanger.
According to an alternative embodiment, the cryotechnic fluid, and in particular hydrogen, is used to carry out the heat exchanges inside the exchangers with the flow of derived air.
According to an alternative embodiment, the flow of depleted air is used to carry out the heat exchanges inside the exchangers with the flow of derived air.
The present invention aims also to propose a device for collecting oxygen-enriched air during a phase of aerobic flight of a space launch rocket and which is intended to be used for combustion inside at least one cryotechnic rocket engine beyond the atmosphere. The launch rocket comprises at least one engine of a turbofan type. The turbofan engine is preferably a twin-spool and twin-flow engine. The engine comprises a high-pressure spool consisting substantially of a high-pressure compressor, a combustion chamber and turbines. The engine also comprises a low-pressure spool surrounding the high-pressure spool, consisting substantially of a blower for collecting the external fluid and in particular air, and a low-pressure turbine, optionally followed by an after-burning area and a variable-geometry nozzle. The engine comprises an exchanger, and a separator with which is combined a cooling unit/condenser assembly. The exchanger, separator and the cooling unit/condenser assembly are arranged directly downstream of the blower in order to use the air coming out from the blower in the form of a derived flow. The blower collects the derived flow and separates it into a flow of oxygen-enriched air and a flow of oxygen-depleted air.
Advantageously, a second exchanger is placed upstream of the blower.
Preferably, the blower of the turbofan engine has a physical separation so as to separate the main flow from the derived flow.
An alternative aspect of the present invention aims to propose a twin-spool and twin-flow engine of turbofan or turbocompressor type. The engine comprises a high-pressure spool consisting substantially of a high-pressure compressor, a combustion chamber and turbines, and a low-pressure spool surrounding the high-pressure spool, consisting substantially of a blower for collecting the external fluid and in particular air, and a low-pressure turbine. The low-pressure turbine may be optionally followed by an after-burning area and a variable-geometry nozzle. The blower may comprise two or three low-pressure stages and may comprise fins installed on its vanes and separations installed on its rectifiers so as to separate the derived flow from the main flow.